11 Bg3 seems best. Why relieve Black's defense by swapping pieces ?
A more common motif on move 13 would be Rb1, b4 and b5. If 13 .....a5, then 14 a3 to still get in 15 b4. This is called a minority attack, where Black's c6 pawn can turn out very weak.
I played this game today and lost. I felt quite good out of the opening, but I have a tendency of building a slight advantage and then giving it away in the middlegame. So any tips on how I could have gone about this game differently would be great!